The present invention relates to a coupling bearing for rotors running above critical speed, with the bearing enclosing the rotor and being connected and disconnected depending on radial rotor movements.
In the attempt to operate in the turbine, compressor and related fields with rotors of continuously increasing speeds, nominal speed ranges have been reached which are above the critical speed for bending of the rotor. Attempts have been made to push the rotor through the critical speeds by starting it with intensified driving force. This has been successful only with very well balanced rotors, so that the emphasis of stabilizing efforts is concentrated on bearing technology. In this connection, the so-called coupling bearing is gaining increased importance.
During quiet running of the rotor, coupling bearings do not perform a bearing function; they start to operate only at higher vibration amplitudes by being mechanically coupled as a result of rotor deflections.
A coupling bearing, in contrast with the usual damping bearings carrying and supporting the rotor, acts as an auxiliary bearing by entering action only for short periods, when the critical speed ranges are being used.
While the rotor starts to run in the coupling bearing, energy is withdrawn from the rotor via the damper connected to the coupling bearing, and the natural frequency of the system is changed by coupling the coupling bearing mass. Due to both circumstances, the rotor cannot deflect unduly, and as the rotor speed increases, the rotor leaves the critical range earlier.
The effectiveness of a coupling bearing depends on various factors among which are the point in time when the bearing takes over and its response readiness.
Other requirements on a coupling bearing are made in view of the required high rotary speeds of the rotors. It is necessary that the drive energy withdrawal be kept as low as possible. For this reason, the coupling bearing-rotor system should have no friction during the periods between the critical speeds, particularly in the nominal range, and should have low friction during use of the bearing.
It is, therefore, an object of the present invention to provide a coupling bearing of the above-described type which, besides a very short response time, ensures frictionless free-running of the rotor.
Another object of the present invention is to provide a coupling bearing of the foregoing character which is substantially simple in construction and may be economically fabricated.
A further object of the present invention is to provide a coupling bearing, as described, which may be readily maintained in service and which has a substantially long operating life.